Physical failure analysis method for semiconductor tungsten wire contact window

Abstract

The present invention belongs to the field of semiconductor integrated circuit manufacturing. Provided is a PFA method for a semiconductor tungsten wire contact window (W KH). The PFA method of the present invention comprises: a cutting step of cutting, into a PFA test piece, a portion of a wafer that requires PFA; a coating step of using a mark pen to perform coating on a cross section of the PFA test piece; and an observation step of using an SEM to observe the cross section. The PFA method provided in the present invention can avoid damage to an element structure of the cross section of the PFA test piece during the preparation of the PFA test piece, so that PFA can be accurately performed.

Description

Physical Failure Analysis Method for Semiconductor Tungsten Wire Contact Window Technical Field

[0001] The present invention relates to the field of semiconductor integrated circuit manufacturing, and in particular to a physical failure analysis method for a semiconductor tungsten wire contact window. Background Art

[0002] In semiconductor integrated circuit manufacturing, wafers undergo tests such as the Wafer Acceptance Test (WAT) after all or part of the manufacturing process is complete. If an anomaly is detected in the tungsten contact hole (WKH) on the wafer during WAT, a physical failure analysis (PFA) is performed on the abnormal area to identify the cause of the anomaly.

[0003] Existing PFA processes typically include the following steps: a dicing step, where the portion of the wafer to be PFAed is cut into PFA coupons; a coating step, where a layer of carbon (C) is deposited on the cross-section of the PFA coupon; and an observation step, where the cross-section of the PFA coupon is observed using a SEM (scanning electron microscope). The purpose of the C coating on the cross-section of the PFA coupon is to make the cross-section of the PFA coupon conductive, allowing for subsequent SEM (Scanning Electron Microscopy) observation of the cross-section of the PFA coupon. Furthermore, for tungsten contact windows, C coating on the cross-section of the PFA coupon also enhances the clarity of the device structure interfaces during SEM observation. In existing technology, C coating is typically performed using an E-beam (electron beam evaporation) method. However, this E-beam coating method can cause deformation of the device structure in the cross-section of the tungsten contact window (WKH) PFA coupon, resulting in defects in previously non-defective locations, which can interfere with subsequent observation steps.

[0004] Therefore, a method for accurately performing PFA on tungsten wire contact windows (W KH) is urgently needed without damaging the component structure of the PFA specimen cross section. Technical issues

[0005] The present invention aims to provide a method for accurately performing PFA on a tungsten wire contact window (WKH) PFA test piece without damaging the component structure of the cross section. Technical Solutions

[0006] The PFA method of the present invention comprises:

[0007] a cutting step of cutting the portion of the wafer that needs to be subjected to the physical failure analysis into physical failure analysis test pieces;

[0008] a coating step of coating the cross section of the physical failure analysis specimen where the physical failure analysis is required with a marker pen; and

[0009] In the observation step, the cross section is observed using a scanning electron microscope. Beneficial effects

[0010] The PFA method provided by the present invention can avoid damage to the component structure of the cross section of the PFA test piece during preparation, thereby enabling accurate PFA. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIG1 is a flow chart of a PFA method of the present invention;

[0012] FIG2 is a schematic top view of a wafer of the present invention; and

[0013] FIG3 is a schematic cross-sectional view of the PFA test piece of the present invention along the AA′ direction in FIG2 .

[0014] Explanation of symbols

[0015] 1 wafer

[0016] 2 PFA test pieces

[0017] 3 Tungsten wire contact window

[0018] 4 Cross-sections requiring PFA Best Mode for Carrying Out the Invention

[0019] The PFA method of the present invention is described below with reference to Figures 1 to 3. As shown in Figure 1, the PFA method of the present invention includes: a cutting step S001, a coating step S002, and an observation step S003. Each step will be described in detail below.

[0020] In the cutting step S001, the portion of the wafer 1 that needs to undergo PFA is cut into a PFA test piece 2. In this embodiment, as shown in FIG2 , at the location where the abnormal tungsten wire contact window 3 is located, cutting is performed in a direction perpendicular to the wafer surface, and the abnormal tungsten wire contact window 3 and its surrounding portion are cut into a PFA test piece 2. FIG3 is a schematic cross-sectional view of the PFA test piece 2 along the A-A' direction in FIG2 . It should be noted that, for simplicity, only one layer is drawn above and below the tungsten wire contact window 3 in FIG3 , but in fact, there can be many layers above and below the tungsten wire contact window 3. The PFA test piece 2 can be formed using cutting methods commonly used in the art, which will not be described in detail here.

[0021] In coating step S002, a marker pen is used to coat cross section 4 of PFA specimen 2 where PFA is to be applied. Because marker ink also contains C, coating cross section 4 with the marker pen also forms a thin film of C on cross section 4. This has the same effect as applying C to cross section 4 using an E-beam. Furthermore, coating with a marker pen does not damage the device structure in cross section 4, preventing defects from appearing in previously defect-free locations. This also prevents interference during subsequent SEM observation.

[0022] In the observation step S003, the cross section 4 is observed using a SEM to find out the cause of the abnormality. The method of the observation step S003 is the same as that in the prior art, and thus will not be described in detail.

[0023] The PFA method provided by the present invention can avoid damage to the component structure of the cross section of the PFA test piece during preparation, thereby enabling accurate PFA.

[0024] Although the present invention has been disclosed in the form of embodiments as described above, they are not intended to limit the present invention. Any professional and technical personnel in this field may make various necessary changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be based on the scope defined by the attached claims.

Claims

1.

1. A physical failure analysis method for a semiconductor tungsten wire contact window, comprising: Cutting step S001, cutting the portion of the wafer (1) that needs to be subjected to the physical failure analysis into physical failure analysis test pieces (2); A coating step S002, coating with a marker pen on the cross section (4) of the physical failure analysis specimen (2) where the physical failure analysis is to be performed; and Observation step S003: observing the cross section (4) using a scanning electron microscope.

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